This invention relates to an automatically-operating valve intended to close off a flow passage through the valve in the event that the valve is subjected to a significant impact. In particular, but not exclusively, the invention concerns a valve for use in connection with the mounting of a forecourt liquid fuel dispensing pump on to a supporting base.
Fuel pumps for dispensing petrol or diesel fuel into the tank of a motor vehicle generally comprise a self-contained unit mounted on a base or plinth on a garage forecourt, the pump being connected by way of a pipeline to an underground storage tank from which the fuel is drawn during operation of the pump. Some fuel pumps operate simply by suction, so that there is a sub-atmospheric pressure in the pipe from the underground tank to the pump, whenever the pump is in operation. Other installations employ a pressure-feed system where fuel in the pipeline from the tank to the pump is under pressure, to ensure a uniform delivery of fuel to the pump. A pressure-feed system is usually employed when there is a relatively long pipeline from the underground tank to the pump.
Not infrequently, vehicles manoeuvring on a garage forecourt collide with a fuel pump and displace the pump from its proper position on its base or plinth. In order to prevent significant fuel spillage (which could be most substantial in the case of a pressure-feed system) it is the usual practice to fit a shear valve in the pipeline delivering fuel to the pump, in the vicinity of the mounting of the pump on to the base or plinth. A basic example of such a shear valve is shown in U.S. Pat. No. 3,489,160 and a much improved form in WO 96/17191. In both these prior valves, there is a weakened zone in the valve body so that if the pump is subjected to a lateral displacement, the valve will shear across its weakened zone. An automatically-operating valve member provided within the shear valve then closes the delivery pipeline to prevent leakage of fuel. In the improved valve of WO 96/17191, operation of the valve member is controlled by a relatively weak frangible link, so that even a minor impact insufficient to displace the fuel pump from its normal position but still sufficient to crack the valve body about its weakened zone will break the frangible link and so cause the valve to close.
Though the improved valve of WO 96/17191 greatly increases safety on forecourt installations and can minimise environmental damage, nevertheless it is still possible for damage to occur to a fuel pump which does not move the pump with respect to its base or plinth and so which does not break the shear valve so causing the valve to close, but which does still allow liquid fuel to escape. For example, when the pump is operating a flexible hose connecting the pump to a delivery nozzle could become damaged or even torn away from the pump, allowing a sudden and excessive outflow of fuel. In addition, component parts of the pump mechanism itself could fail, so allowing an excessive outflow of fuel.
It is a principal aim of the present invention to address the above described problem and so to provide a valve which is capable of operating to close a flow passage therethrough in the event that a problem arises which, if not addressed, would allow excessive outflow of liquid downstream of the valve.
According to the present invention, there is provided a valve having a body defining a flow passage within which is formed a valve seat, the valve body having a weakened zone around the flow passage whereby an impact may fracture the body at the weakened zone, a valve member engageable with the valve seat and movable within the flow passage to open and close the valve, and closing means to effect movement of the valve member to close the valve upon the valve body being fractured at the weakened zone, the valve member being arranged to move to its closed position under the influence of excessive flow though the flow passage.
The valve of this invention will hereinafter further be described particularly with reference to its intended use with a forecourt liquid fuel pump, though the invention is not to be regarded as limited to that use and may be employed in other industriesxe2x80x94for example, in a chemical manufacturing plant.
The valve of the present invention operates on an automatic basis, to close the flow passage through the valve body in the event that an impact on the valve fractures the body around its weakened zone. In this respect, the valve may be similarly arranged to those described in U.S. Pat. No. 3,489,160 or WO 96/17191. However, in addition the valve member is arranged to move to its closed position, so as to close the passage through the housing, in the event that the liquid flow rate through the valve exceeds a pre-set value. Thus, should some problem arise with the fuel pump so allowing the outflow of fuel but which nevertheless does not break the housing at its weakened zone, the valve will still close and thus prevent further outflow of liquid.
Movement of the valve member to its closed position under the influence of excessive flow could be achieved in a number of different ways. For example, it would be possible to provide a flow rate monitor (such as an impeller) the output of which is used to control an actuator associated with the valve member so as to close the valve when an excessive flow rate occurs. The preferred arrangement is for the valve member directly to be closed by an excessive liquid flow rate, by appropriate configuration of the valve member and its associated components mounting the valve member within the passage. For example, a spring may be provided which biases the valve member to its open position and the valve member partially obstructs the flow passage when the valve member is in its open position, such that flow past the valve member in the direction of closing movement thereof exerts a force on the valve member tending to close the valve against the action of said spring. In one embodiment, the valve member and seat are in the form of a poppet valve with the valve member mounted for sliding movement towards and away from the valve seat. Then, by appropriately configuring the head of the poppet valve member, increasing flow rates may exert increasing forces on the valve member so as gradually to move the valve member against the action of the spring until the valve is closed.
For such an arrangement, the closing means (which effects movement of the valve member in the event of fracturing of the body) may include a lever external to and pivoted to the valve body and which is released on fracturing of the body. Such a lever may be connected to a cam internally of the flow passage, the cam being configured to move the valve member to its closed position against the action of the spring, on pivoting movement of the lever.
An alternative arrangement to a sliding poppet valve is for the valve to be in the form of a flap valve having a valve member which hinges within the passage, to co-operate with the valve seat when in its closed position. Such a valve member should be associated with a spring to bias the valve member to its open position. Again, by having the valve member partially obstructing the flow passage when the valve is open and by appropriate configuration of the valve member, increasing flow through the passage will exert a closing force on the plate, so moving the plate against the action of the spring until the valve eventually closes.
As with the arrangement employing a poppet valve, the closing means for effecting movement of the valve member to its closed position on fracturing of the valve body may include a lever external to and pivoted to the body and which lever is released on fracturing of the valve body. Such a lever may be connected to the flap valve member internally of the flow passage, to effect closing movement thereof. Conveniently, the arm carrying the valve member is mounted for pivoting movement about the same axis as that of the lever; in this case, a spring-loaded toggle mechanism may interconnect the lever and the arm, whereby movement of the lever through an over-centre position of the toggle mechanism will drive the flap valve member to its closed position. The spring of such a toggle mechanism may also serve to bias the valve member to its open position prior to fracture of the valve body and so prior to releasing the lever, whereby the arm may move the valve plate to its closed position under excessive flow conditions against the action of that spring of the toggle mechanism.
In either case described above, there may be a second spring which urges the lever of the closing means to a second position where the valve is closed, from a first position where the valve is open but the valve member is free to move under excessive flow conditions. The lever is normally held in said first position by a release mechanism which frees the lever should the valve body break at its weakened zone. Such a release mechanism may be substantially as described in WO 96/17191, where a frangible link bridges the weakened zone of the valve body and which link breaks to free the lever in the event that the valve body fractures at its weakened zone.
The valve of this invention may be provided with a second valve seat within the flow passage on the other side of the weakened zone with respect to the first-mentioned valve seat, there being a second valve member mounted to co-operate with that second valve seat. Such a second valve member and seat may form a simple non-return valve which is arranged to close under no-flow or reverse flow conditions, having regard to the normal intended flow direction through the valve. In the alternative, the second valve seat and member may be of a similar construction and arrangement to the first-mentioned valve seat and member, but acting in the opposite sense with respect to the first-mentioned valve seat and member. In this case, both valves will be closed in the event that the valve body fractures about its weakened zone, so preventing leakage of fuel from the fuel pump, as well as from the pipeline supplying the pump, in the event that the valve body is subjected to an impact sufficient to fracture the housing.